Conventionally, a run-flat tire that may travel in a certain long distance when punctured (hereinafter, such a traveling is called as “run-flat traveling”) is well known. The run-flat tire usually has a side reinforcing rubber layer with a crescent cross-sectional shape in each sidewall portion. In order to improve run-flat performance of the tire, a run-flat tire having a side reinforcing rubber layer with a large volume is proposed. The run-flat tire, however, is liable to deteriorate ride comfort and fuel consumption due to its increased spring constant and mass.
Furthermore, a vehicle usually has rear wheels with a negative camber alignment. Thus, the run-flat tires installed on the rear wheels of the vehicle are subjected to a large tire load on its inboard, and damage tends to concentrate to the inboard of the tire. On the other hand, the run-flat tires installed on the front wheels of a vehicle are subjected to large tire load on its outboard when cornering, and damage tends to concentrate to the outboard of the tire.
In view of above, Japanese Unexamined Patent Application Publication mentioned below discloses a run-flat tire having a pair of side reinforcing rubber layers with different thicknesses, which is intended to install to a vehicle so that the side reinforcing rubber layer with the relatively large thickness is disposed on the side of the wheel where damage tends to concentrate (namely, the inboard of the rear wheels, or the outboard of the front wheels).